Chapter 4. Advanced Utilities

In this chapter, we will cover the following topics:

• Building an Ajax chat system using the Comet technique

• Charting with JavaScript

• Decoding Captcha through canvas

• Displaying data in a grid

In this chapter, we're going to look at building a simple Ajax chat application using the Comet technique. Comet is a technique in web applications to push data to the client from a web server without the explicit need for a client to request it. In this application, we will use this simple Comet technique to push the chat message from the server to the browser, without using any special Comet server for it.

In the Charting with JavaScript section, we will look at how to use the Google Visualization API to build an interactive chart using JavaScript.

After that, we're going to show you how Ajax programming with canvas can decode a simple Captcha on the browser itself, using a Firefox Greasemonkey script.

Note

The chat application used here doesn't use any Comet server such as APE...